The present invention relates generally to sound absorbing systems, and more particularly, to an acoustical attenuation system for a vehicle and a method of manufacturing the same.
Various sound absorbing materials are used throughout a vehicle in order to reduce noise levels within the vehicle cabin. It is desirable for vehicle occupants to experience low noise levels while in the vehicle, especially within a frequency range of approximately 1 KHz and 5 KHz, for which occupants are generally most sensitive.
Sound energy within a vehicle typically consists of both high and low frequency components that propagate through air and can be absorbed and attenuated through many systems or mechanisms. Several materials absorb and attenuate sound through viscous losses, movement or shearing of air in a material, or by sound induced kinetic energy losses within fibers of a material, where sound energy is converted into thermal energy. Materials may experience both viscous and kinetic losses.
Porosity and structural geometry of a material also affect airflow characteristics and resulting sound absorption and attenuation characteristics. The less porous an object, generally the less airflow through the object and the higher the airflow resistance of the object.
Vehicle headliners commonly include various types of sound absorbing and attenuating materials. Headliners are a major contributor in sound absorption and attenuation within a vehicle cabin, second only to vehicle seating systems.
Headliners can be formed of various materials and are designed for ease of manufacturing, weight consideration, durability and economics, as well as sound absorption and attenuation. Current headliners today, have several of the above desired aspects, but provide a limited amount of sound absorption and attenuation due to material properties and overall design.
It would therefore be desirable to provide a vehicle headliner with increased sound absorption and attenuation ability over current headliners while at the same time having other headliner desirable aspects such as being light in weight, relatively easy and inexpensive to manufacture, and durable.
The present invention provides an improved acoustical attenuating system for vehicles, as well as a method of producing them. The attenuating systems include an exterior layer, a sound absorption layer, and multiple perforated layers coupled to the sound absorption layer. The perforated layers include a perforated structural and a perforated substrate layers. The perforated structural layer and the perforated substrate layer provide structural stiffness and define multiple resonating tubes that attenuate sound.
The present invention has several advantages over existing acoustical attenuating devices. One advantage of the present invention is that it provides an acoustical attenuating device, such as a headliner, having multiple layers that are permeable. By controlling permeability, airflow through the attenuating device can be refined, thus providing improved sound absorption.
Another advantage of the present invention is that it has multiple perforated layers defining multiple resonating tubes, which can provide sound absorption at desired frequencies.
Furthermore, the present invention provides an air filter layer for preventing contaminates such as dust and dirt from flowing through the attenuating device.
Moreover, the present invention is versatile in that it is tunable for various frequency ranges. Thus, allowing it to be used in various acoustical attenuating applications.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.